My iPhone 3GS has some problems and now I can't upgrade from 4.1

I really want to upgrade to iOS 5 however a few months ago I started having troubles with my jailbreak and took it to a store to fix it, I'm not very good with technical stuff so I wouldn't have been able to fix it. Anyway I tried upgrading the firmware to iOS 5 and it upgraded however didn't recognise my simcard, I tried numerous sim cards however it says 'searching' and nothing more. I took it back a few days ago, I recently had my bank account froze (by my parents) so can't afford an upgrade and being on 4.1 is okay however some apps require 4.2 or higher which is annoying. I'd really appreciate some help to be honest, like I said I'm not great with tech or sure if I've gave enough information however I'll post any if required